Various synthetic fluids, including synthetic hydrocarbons and silahydrocarbons, have been developed which are useful in the formulation of hydraulic fluids and lubricants which are stable at high temperatures. Tetraalkylsubstituted silanes have been proposed for use in the formulation of hydraulic fluids and lubricants since they possess excellent viscosities over a wide temperature range, low pour points, and exhibit excellent thermal stabilities.
Various methods have been proposed for synthesizing tetraalkylsilanes involving the addition of a Grignard reagent or alkyllithium compounds to alkyltrichlorosilanes. Such processes are described in U.S. Pat. No. 4,367,343 to Tamborski et al; Rosenberg et al, J. Org. Chem., 1960, Vol. 25, pp. 243-248; and Baum et al, J. Chem. Eng. Data, 1961, Vol. 6, No. 1, pp. 142-145.
Reaction of alpha-olefin with triethylsilane to form vinylsilanes and allylsilanes using rhodium complexes is described by Millan et al, J. C. S. Chem. Comm., 1981, pp. 673-674. The use of a rhodium catalyst is described as producing, at best, 90 percent saturated product with the remainder being unsaturated silahydrocarbons at a total yield of 40 percent. Conditions producing higher total yields gave about 50 percent unsaturated products. The presence of unsaturation in the silahydrocarbon molecule has been considered highly undesirable when such compounds are to be used in the formulation of hydraulic fluids and lubricants. Olefinic compounds cause color formation during storage, and lead to formation of gums and sludge in engines as well as premature oxidation. Normally, such unsaturated products would have to be subjected to hydrogenation, at additional expense, to provide the corresponding saturated product.